This invention relates generally to data communications with a trailer and, more specifically, to data communications systems and methods for monitoring and controlling subsystems on a trailer.
The trucking industry has for many years used tractor/trailer combinations to transport cargo over the roadways to intended destinations. As shown in FIG. 1, tractor 10 and trailer 20 are mechanically coupled together so that the tractor can pull the trailer with its cargo in an efficient and cost effective manner. Various links between the tractor and the trailer provide vehicle subsystems with power and/or control signals to operate. Hydraulic, pneumatic, electrical and other subsystems on the tractor/trailer combination have associated electrical conductors and pneumatic lines running therebetween so these subsystems can operate. With respect to electrical subsystems, a tractor/trailer combination typically includes a tractor 10 and trailer 20 and a power bus 30 electrically connected to one or more batteries 32, which are typically charged by an alternator 34 mechanically driven by a tractor engine 15. Thus, electrical power is distributed from tractor 10 to subsystems in trailer 20.
The trucking industry has historically lagged behind other industries with respect to technological innovation, but recently has been incorporating more and more sophisticated electronic subsystems in both tractors and trailers. For example, regulatory changes arising from safety concerns have led to the incorporation of trailer antilock braking systems (ABS), frequently microprocessor-controlled, in trailers in order to minimize the risk of trailer skids and jackknifing. New trailers are being constructed with ABS, while older trailers are being retrofitted to incorporate ABS. These systems may include, for example, actuators and transducers operatively connected to the trailer wheels and braking hardware, controlled by electronic circuits located elsewhere on the trailer and tractor. As shown in FIG. 1, an antilock braking system 100, as well as other subsystems, conventionally receives electrical power from power bus 30.
Antilock braking systems may produce data signals which indicate various conditions of the ABS. These data signals may include, for example, a failure warning signal which is asserted if an ABS microprocessor detects a failure within itself or other components of the ABS. In some applications, a data signal may drive a light-emitting diode (LED) or other indicator. Conventionally, the tractor/trailer operator has no external indication of the state of the ABS. Even those systems having an external indicator may not allow a tractor/trailer operator to inspect the state of the ABS while positioned in the tractor cab with the tractor/trailer combination in operation. The operator typically may have to park the vehicle, exit the cab, and inspect an ABS indicator on the trailer, if present, in order to monitor the state of the ABS. Thus, it may be difficult for the operator to monitor the state of the ABS system while the vehicle is moving.
It may be possible to wire data signals from an ABS to a tractor using a dedicated signal path such as a twisted wire pair passed from the trailer to the tractor. A seven-pin connector has been widely used by the trucking industry to convey electrical power for lighting and equipment operation between a tractor and a trailer. As shown in FIG. 2, the connector 40 includes two disengageable connector portions 50 and 60 to permit the tractor and trailer combination to be disconnected. An example of such a seven-pin connector is illustrated in U.S. Pat. No. 4,969,839 to Nilsson, the entire disclosure of which is specifically incorporated herein by reference. These seven-pin connectors are well known and have been specified by the Society of Automotive Engineering (SAE) according to the standard number xe2x80x9cSAE J560xe2x80x9d, the teachings of which are also incorporated herein by reference.
Each of the sockets 54 in the standard seven-pin connector (SAE J560) is an electrical conductor carried by the plug portion 50 of the connector and which is adapted to mate with a corresponding electrical pin 63, also an electrical conductor, in the receptacle portion 60 of the connector to thereby provide an electrical signal between the tractor and the trailer. The pins and corresponding sockets generally are assigned to specific electrical subsystems, for example, power, ground, turn signals, brake lights, clearance lamps, emergency flashers, and other devices requiring electrical signals.
Until recently, the seventh pin on the connector has been an xe2x80x9cauxiliaryxe2x80x9d pin which could be used for specific electrical purposes or applications on individual tractor/trailer combinations. Pursuant to Federal Motor Vehicle Safety Standard No. 121, however, the National Highway Traffic Safety Administration has mandated that the antilock braking systems of all trailers on the road after Mar. 1, 1998 must not only be powered by the power line that drives the brake lights, but also by a second power line that is connected to the tractor by means of the seventh pin, i.e., the former auxiliary pin. As a result, all seven pins of the connector will soon be dedicated to a particular purpose.
Although pins and sockets of the seven-pin connector may be used to convey an ABS status signal to a tractor, the generally limited circuit capacity afforded by the standardized connector would be reduced even further. The standard seven-pin connector simply may not provide the circuit capacity needed to convey to a tractor an increased number of data signals from various systems located on trailers, including additional ABS systems which may be present when a tractor is connected to multiple trailers. Connectors with greater capacity could be employed, but the seven-pin connector (SAE J560) is an industry standard for tractor/trailers. Alternative communications techniques such as fiber optic links or radio communication through free space may bypass the bottleneck of limited channel capacity in the standard connectors used to connect tractors and trailers, but may require the installation of complex and expensive electronic components. These components, often referred to as xe2x80x9cblack boxes,xe2x80x9d may be vulnerable to theft and vandalism when placed on trailers which often are under the control of multiple operators and left in unsecured areas.
In view of the foregoing, it is therefore an object of the present invention to provide systems and methods for data communications in a tractor and/or a trailer.
It is another object of the present invention to provide data communications systems and methods which utilize existing wiring on tractors and trailers.
It is another object of the present invention to provide data communications systems and methods that are also compatible with standardized connectors widely used in the trucking industry.
It is another object of the present invention to provide data communications systems which are less sensitive to the interference and noise frequently present in tractor and trailer electrical systems.
It is another object of the present invention to provide systems and methods for monitoring a warning system of a tractor/trailer combination.
It is another object of the present invention to provide systems and methods for monitoring an antilock braking system of a tractor/trailer combination by a tractor/trailer operator positioned in a cab of a tractor.
It is another object of the present invention to provide systems and methods for monitoring an antilock braking system which allow a trailer equipped with elements of an antilock braking system monitoring system to be used with a tractor which is not equipped with complementary elements while still providing an indication of a status of the antilock braking system to a tractor/trailer operator positioned within the tractor cab.
It is another object of the present invention to provide systems for monitoring an antilock braking system in a tractor/trailer combination using components packaged to be inconspicuous and less vulnerable to theft and vandalism.
It is another object of the present invention to reliably communicate with a number of subsystems positioned on one or more trailers.
These and other objects, features and advantages of the present invention are provided according to one embodiment by systems and methods for communicating antilock braking signals to a status indicator via the power bus which distributes power to the antilock braking system. Thus, a vehicle according to the embodiment includes a tractor connected to a trailer having an antilock braking system and an antilock braking system interface which produces a data signal, typically representing the status of the antilock braking system. The vehicle also has an ABS reporting system that receives the data signal and includes power line carrier communicating means, responsive to the antilock braking system, that produces a data communications signal representing the status of the antilock braking system over the power bus. The vehicle of this embodiment also includes status determining means for determining the status of the antilock braking system from the data communications signal. The status determining means preferably includes an indicator which indicates the determined status to a tractor/trailer operator positioned within the cab of the tractor.
The present invention provides for remote monitoring an antilock braking system by a tractor/trailer operator. Thus, the present invention allows a tractor/trailer operator to monitor an antilock braking system while the operator is positioned in the tractor cab and the tractor/trailer combination is in motion. The present invention also provides for monitoring of the status of an antilock braking system without requiring extensive rewiring of the tractor or the trailer. Furthermore, the present invention provides for monitoring of an antilock braking system using existing power wiring and connectors.
According to one embodiment, the power line carrier communicating means may include a waveform generator, preferably an oscillator, which produces a power line carrier signal having a predetermined carrier frequency. A modulator is responsive to the waveform generator and the antilock braking system and produces the data communications signal from the power line carrier signal and the data signal. Coupling means couples the modulator to the power bus and superposes the data communications signal on the power bus.
The status determining means may include power line carrier receiving means that is responsive to the power bus and receives the data communications signal. Processing means is responsive to the power line carrier receiving means and produces a data-modulated digital carrier signal from the received data communications signal. Detecting means detects a status of the antilock braking system from a count of the transitions of the data-modulated digital carrier signal occurring during a predetermined time interval. The status determining means may also include an indicator for indicating the determined status to a tractor/trailer operator positioned within a cab of the tractor, thus informing the operator of the condition of the antilock braking system while the tractor/trailer combination is in operation. The indicator may be in the form of lights, gauges, images on a CRT screen, audible annunciators and the like, as would be readily understood by those skilled in the art.
The power bus may include a plurality of tractor power lines and trailer power lines electrically connected by a connector. The connector may include an industry-standard SAE J560 connector. Thus the present invention provides for monitoring of an antilock braking system using existing wiring and connectors.
According to one advantageous embodiment, the power bus also includes a first capacitor disposed between at least two of the tractor power lines and a second capacitor disposed between at least two of the trailer power lines. By placing the data communications signal on one of the capacitively coupled power lines, the data communications signal is transmitted via each of the capacitively coupled conductors. As a result, the communications system of this embodiment provides redundancy.
In another aspect of the present invention, the power line carrier communicating means may be integrated with a warning indicator in a trailer warning indicator package. The warning indicator is responsive to the antilock braking system interface and indicates a status of the antilock braking system from the data signal. The trailer warning indicator package includes means for mounting the trailer warning indicator package so that it is positioned on the trailer and is viewable by a tractor/trailer operator positioned within the tractor cab. Thus, a trailer which incorporates the power line carrier communicating means of an antilock braking system according to the present invention may be used with a tractor which is not equipped with the complementary status determining means, while still providing a way to indicate a status of the trailer antilock braking system to a tractor/trailer operator positioned within the tractor cab. The trailer warning indicator package preferably has a standard form factor, such as that of the standard running lights commonly used on trailers, thereby providing components of an antilock braking system monitoring system which are inconspicuous and less susceptible to vandalism and theft.
According to another aspect of the present invention, a communications system for communicating the status of a subsystem positioned on a trailer to a tractor is provided that includes a power bus which supplies electrical power to the combination of the tractor and the trailer, and spread spectrum signal producing means, responsive to the subsystem and positioned on the trailer, for producing a spread spectrum data communications signal representing the status of the subsystem on the power bus. For example, the subsystem may produce a status signal representing a status of the subsystem, and the spread spectrum signal producing means may include means for producing the spread spectrum data communications signal from the status signal. Status determining means, positioned on the tractor, is responsive to the power bus for determining the status of the subsystem from the spread spectrum data communications signal. The status determining means may include spread spectrum signal receiving means, positioned on the tractor and responsive to the power bus, for receiving the spread spectrum data communications signal, and means, positioned on the tractor and responsive to the spread spectrum signal receiving means, for determining the status of the subsystem from the received spread spectrum data communications signal. The status determining means also preferably includes an indicator, such as an alphanumeric display, an a LED display, or an audio annunciator, which indicates a status of the subsystem to an operator positioned in the tractor.
According to another aspect, a communications system is provided for permitting a tractor and a trailer mechanically and electrically connected to the tractor to communicate a command from the tractor to a subsystem positioned on the trailer. According to this embodiment, the communications system includes a power bus which supplies electrical power to the combination of the tractor and the trailer, spread spectrum signal producing means, positioned on the tractor, for producing a spread spectrum data communications signal representing the command on the power bus, and controlling means, positioned on the trailer, for controlling the subsystem based on the spread spectrum data communications signal. The controlling means preferably includes spread spectrum signal receiving means, positioned on the trailer and responsive to the power bus, for receiving the spread spectrum data communications signal, and means for controlling the subsystem from the received spread spectrum data communications signal. The system also preferably includes operator input means for receiving a command from an operator positioned on the tractor, such as via a switch mounted on an instrument cluster in the tractor.
Thus, the communications system of the present invention can provide commands to the various subsystems on the trailer. These commands may be provided by the operator of the tractor/trailer combination or may be automatically generated, such as according to a predetermined schedule or in response to a particular event. Among other things, the command may request that one or more subsystems provide status or other data. In addition to responding to commands, the subsystems themselves may initiate communications, such as with other subsystems in the trailer or tractor, if so desired.
According to the present invention, a communications module designed to be mounted to a trailer can communicate via a power bus and includes a status signal input and a command signal output. The communications module includes spread spectrum signal producing means, responsive to the status signal input, for producing a spread spectrum data communications signal from a status signal provided at the status signal input. The spread spectrum signal producing means is coupled to the power bus such that the spread spectrum data communications signal is superposed on the power bus. The communications module also includes spread spectrum signal receiving means for receiving a spread spectrum communications signal superposed on the power bus and for producing a command signal at the command signal output from the received spread spectrum communications signal. The communications module also preferably includes a communications module housing which houses the spread spectrum signal receiving means and the spread spectrum signal producing means. Typically, the communications module housing is mounted to the trailer.
Likewise, one embodiment of the present invention also provides a communications module designed to be mounted within the tractor that communicates via the power bus and which includes a command input. The communications module of this embodiment also includes spread spectrum signal producing means, responsive to the command input, for producing a spread spectrum data communications signal from a command provided at the command input. The spread spectrum signal producing means is coupled to the power bus such that the spread spectrum data communications signal is superposed on the power bus. The communications module also includes spread spectrum receiving means for receiving a spread spectrum data communications signal superposed on the power bus that typically represents the status of a respective subsystem. The communications module also preferably includes status determining means, responsive to the spread spectrum receiving means, for determining the status of the subsystem from the received spread spectrum data communications signal. In this regard, the status determining means preferably includes an indicator which indicates the status of the subsystem. The communications module also preferably includes operator input means for receiving a command from an operator, such as via a switch. The communications module also preferably includes a communications module housing which houses the spread spectrum signal producing means, the spread spectrum signal receiving means, the indicator and the operator input means, and means for mounting the communications module on the tractor such that the indictor is viewable by and the operator input means is accessible to an operator positioned in the tractor.
The power bus may oftentimes supply power to a number of subsystems on one or more trailers. According to one particularly advantageous embodiment, the communications system is designed to communicate or otherwise broadcast the respective status of each of the plurality of subsystems positioned on at least one trailer to the tractor even though the subsystems communicate according to at least two different protocols. For example, the subsystems can include an antilock braking system that communicates according to a J-1708 protocol and a refrigeration unit that communicates according to an RS-232 protocol. According to this embodiment, the spread spectrum signal producing means preferably includes a plurality of protocol specific transmitters associated with respective ones of the subsystems. Each protocol specific transmitter receives signals from the respective subsystem that have a predetermined protocol and converts the signals to a standardized format. For example, the protocol specific transmitters can include an RS-485 transceiver associated with an antilock braking system for receiving J-1708 signals and an RS-232 transceiver associated with a refrigeration unit for receiving RS-232 signals. The spread spectrum signal producing means of this embodiment also preferably includes means for producing spread spectrum data communications signals representative of the status of respective ones of the subsystems based upon the standardized signals that are provided by the protocol specific transmitters. Based upon the spread spectrum data communications signals, the status determining means of the communications system of this embodiment can determine the status of respective ones of the subsystems.
In one embodiment, the protocol specific transmitters are protocol specific transceivers. As such, the protocol specific transceivers preferably include means for determining the state of the respective transceiver such that signals transmitted by the protocol specific transceiver are not also received and processed by the protocol specific transceiver.
According to another embodiment of the communications system that communicates the respective status of each of a plurality of subsystems positioned on at least one trailer to the tractor, the spread spectrum signal producing means includes a plurality of spread spectrum transmitters responsive to respective ones of the subsystems for producing spread spectrum communications signals representing the status of the respective subsystems. The spread spectrum signal producing means of this embodiment preferably includes self-diagnostic means for monitoring the signals provided to the spread spectrum transmitter by the protocol specific transmitters and for halting further transmission by the spread spectrum signal producing means to the communications system if the self-diagnostic means determines that the signals provided to the spread spectrum transmitters are inaccurate or otherwise includes errors. As a result, the remainder of the communications system can continue to operate as designed without being corrupted by inaccurate signals.
In order to permit the communications system of the present invention to effectively broadcast a spread spectrum data communications signal representing the status of a first subsystem on the power bus, the communications system of one advantageous embodiment further includes spread spectrum blocking means associated with respective ones of the other subsystems. The spread spectrum blocking means protect the spread spectrum data communications signal placed on the power bus by the spread spectrum signal producing means from attenuation by the other subsystems. In one embodiment, the spread spectrum blocking means includes a plurality of inductive elements associated with respective ones of the other subsystems. Alternatively, the spread spectrum blocking means can include a plurality of ferrite beads associated with respective ones of the other subsystems. In either embodiment, the spread spectrum blocking means is designed to prevent or at least significantly reduce the filtering or other attenuation of the spread spectrum data communications signals by the other subsystems electrically connected to the power bus. As such, the status determining means of the communications system can receive and process a spread spectrum data communications signal without concern that the spread spectrum data communications signal has been significantly attenuated or otherwise distorted by the other subsystems.
The power bus also typically supplies electrical power to a plurality of electrical loads within the tractor. In order to prevent attenuation or other distortion of the spread spectrum data communications signals by the plurality of other electrical loads within the tractor, the spread spectrum signal producing means is preferably electrically connected to a conductor of the tractor power lines at a point nearer the connector than the respective points at which the plurality of electrical loads are electrically connected to the power bus. More particularly, the communications system of this embodiment can include a capacitor disposed between the spread spectrum signal producing means and the respective tractor power line to couple the spread spectrum data communications signal to the respective tractor power line.
Monitoring methods according to the present invention are used for monitoring a subsystem, such as an antilock braking system, of a tractor/trailer combination. These methods include the following steps: a data signal, such as a status signal, is provided by the subsystem; a data communications signal is produced from the data signal; the data communications signal is communicated over a power bus; and the status of the subsystem, such as the antilock braking system, is determined from the data communications signal. The step of communicating may include steps of modulating the data signal with a signal having either a predetermined carrier frequency or a predetermined spectrum of carrier frequencies to produce the data communications signal and superposing the data communications signal on the power bus. The step of determining may include the step of indicating the determined status of the antilock braking system to a tractor/trailer operator positioned within a cab of the tractor.
A method for determining the status of an antilock braking system from a data communications signal representing the status of the antilock braking system is also provided by the present invention. The method includes the steps of: receiving a data communications signal representing one status of a subsystem, such as the antilock braking system; producing a data-modulated digital carrier signal from the received data communications signal; and detecting a status of the subsystem, such as the antilock braking system, from a count of transitions of the data-modulated digital carrier signal occurring during a predetermined time interval.